Method of making plasticized glassine paper



Patented Oct. 27, 1936 UNITED STATES METHOD OF MAKING PLASTICIZE GLASSINE PAPER Lewis Dozier, Rhinelander, Wis., assignor to Rhinelander Paper Company,

Rhinelander,

Wia, a corporation of Wisconsin No Drawing. Application May 27, 1936, Serial No. 82,053

Claims.

This invention relates to a method of makin plasticized glassine paper.

It has heretofore been proposed to plasticize glassine and other greaseproof papers by the in- 5 corporation of glyceri'ne and other agents into the paper during the drying operation and while the paper is only partially dried. While such prior method possesses some advantages over the incorporation of a plasticizing agent into a completely dried paper, I have nevertheless found that a superior plasticized sheet can be more economically manufactured by incorporating only a part of the plasticizing material into the web of paper while partially dried and then, after the r paper has been completely dried, incorporating the remaining portion of the plasticizer at the dampener prior to super calendering the sheet to form glassine paper.

The method of my present invention gives a more uniform penetration and an increased transparency. It is particularly economical when a relatively large percent of plasticizer is to be incorporated into the glassine paper, since the percentage of retention of plasticizer on the dampener prior to super calendering is greater than that of plasticizer applied by a size press between V groups of drying cylinders. One of the reasons for this increased economy is that where the plasticizer is applied in the size press, a certain proportion of the plasticizer is absorbed by the clothing of the machine, that is, by the felts, during the drying operation and some of the plasticizer is further likely to adhere to the surfaces of the drier drums or to be squeezed out of the sheet between the drier drums and the felts.

It is therefore an important object of this invention to provide an improved method for the plasticizing of glassine paper, according to which a part of the plasticizing agent is incorporated into paper is still in a moist and only partially dried state, and the remaining portion of the plasticizing agent is incorporated into the sheet prior to the super calendering operation.

It is a further important object of this invention to provide a more economical method of plasticizing glassine paper by the use of a plasticizing composition containing a wetting agent to assist in the penetration of the plasticizer into the sheet.

Other and further important objects of this invention will become apparent from the following description and appended claims.

Glassine paper, as is well known, is a greasethe sheet during the drying operation while theproof paper that has been super calendered. In the course of the manufacture of glassine, after the sheet has been formed from well hydrated stock and has been completely dried, it is passed over a dampener, where 20% and over of water 5 is applied to the sheet, and the wet sheet is then passed through a super calender, where extremely heavy pressure and heat are applied to the sheet to render it more compact and dense and to impart to it a smooth polished surface.

In accordance with the principles of this invention, a certain amount of a plasticizing composition is incorporated into the sheet of paper after it has been partially dried but before being completely dried, andthen a further quantity of 15 plasticizing material is incorporated into the sheet at the dampener prior to super calendering. Incorporation of the plasticizing material into the sheet during the drying operation may satisfactorily be accomplished by passing the sheet 20 through a size press located between sections of the drying cylinders or drums. At the dampener the plasticizing material may be incorporated into the water used in moistening the web of paper before going to the super calenders, and the solu- 5 tion of the plasticizing material may be sprayed or brushed on to the surface of the paper web, or applied thereto in any other suitable manner.

The plasticizing material may suitably comprise a water soluble polyhydric alcohol, such as glyc- 30 erine, mono-, di-, and tri-ethylene glycol, or propylene glycol, a sodium or potassium soap of a fatty acid having more than 10 carbon atoms to the molecule, either saturated or unsaturated, potassium lactate, ethyl lactate, and others. 35 Preferably a hygroscopic sugar or sugar alcohol is included in the plasticizing composition, examples of which include com sugar or other form of dextrose, various forms of levulose, or mixtures of the two as in invert sugar, sorbitol and the like. 40

In order to enhance the penetrating properties of the aqueous plasticizer solution, I also prefer to incorporate into the solution a salt having wetting properties, such as potassium or sodium acetate, potassium or sodium nitrate, or the like 45 and/or an organic wetting agent, such as the sodium salts of alkylated naphthalene, sulphated higher molecular weight alcohols, sulfonated castor oil, pine oil, and the like.

In general, plasticizing compositions of any of the foregoing ingredients may be made up into aqueous solutions of concentrations not to exceed about 40%, and preferably between 10 and 35% by weight of the solution. The percentages of 55 the various ingredients in the composition on a dry basis may suitably be as follows:

After the dry ingredients within the foregoing ranges have been made up into an aqueous solution, between A and 1% lbs. of a wetting agent per 50 gallons of solution are preferably added, although the proportions of wetting agents may be varied considerably depending upon their particular properties.

Satisfactory results are obtained by using the same plasticizer composition and same concentration in aqueous solution both at the size press and on the dampener. If, for instance, a treating solution is prepared containing about 25% of active ingredients by weight of the solution, about 4% of the plasticizer composition by weight of the sheet will be retained from treatment at the size press and about 8% of the plasticizer composition by weight of the paper will be retained as a result of the treatment on the dampener. In each case the percentage of plasticizer retained is on the basis of the finished glassine paper, so that the total amount of plasticizer composition incorporated into the sheet by the two operations will be about 12%. This indicates that the efficiency of retention of plasticizer composition is about twice as high at the dampener as it is at the size press. Consequently, in making highly plasticized sheets, the advantage of plasticizing in two operations, one of which is on the dampener, is obvious.

The most satisfactory plasticizing agent from an economical standpoint is glycerine. Glycerine imparts the desired degree of softness and flexibility to the glassine paper, which, without any plasticizing agent, has a tendency to be brittle and relatively inflexible. The preferred auxiliary plasticizing agent is corn sugar or corn syrup, which has the property of increasing the transparency of the glassine paper and also in aiding its moisture retention. Sodium nitrate increases the penetrative properties of the plasticizing solution, as do also the organic wetting agents above enumerated, thereby resulting in a more thoroughly impregnated and more uniformly plasticized sheet.

A glassine sheet treated in accordance with the method above described is particularly suitable for waxing and lacquering purposes, the sheet retaining its plasticity after being waxed or lacquered and having a higher degree of transparency than paper not so treated.

I am aware that numerous details of the process may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. In the manufacture of glassine paper, the steps of incorporating a plasticizer material comprising glycerine, a monosaccharide and a wetting agent, into a partially dried web of paper on the driers and incorporating a further amountof said plasticizer after said web has been completely dried and during the moistening of said web prior to super calendering the same.

2. In the manufacture of glassine paper, the steps of incorporating a plasticizer material comprising glycerine, dextrose and a wetting agent, into a partially dried web of paper on the driers and incorporating a further amount of said plasticizer after said web has been completely dried and during the moistening of said web prior to super calendering the same.

3. In the manufacture of glassine paper, the steps of incorporating a plasticizer material comprising glycerine, dextrose and sodium nitrate, into a partially dried web of paper on the driers and incorporating a further amount of said plasticizer after said web has been completely dried and during the moistening of said web prior to super calendering the same.

4. In the manufacture of glassine paper, the steps of incorporating a plasticizer into a partially dried web of paper on the driers and incorporating a further amount of said plasticizer after said web has been completely dried and during the moistening of said web prior to supercalendering the same.

5. In the manufacture of glassine paper, the steps of incorporating about 4% of a plasticizer into a web of paper while partially dried and while on the driers and incorporating about 8% of the plasticizer into said web after said web has been completely dried and during the moistening of said web prior to supercalendering the same, said percentages of plasticizer being on the weight of the finished glassine paper.

LEWIS DOZIER. 

